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  • Guide to Cavity Wall Insulation

    What is Cavity Wall Insulation?

    Cavity wall insulation is injected into the cavity between the inner and outer leaves of brickwork that make up the external wall of your property. An installer will do this from the outside of your property. There are a variety of different insulating materials, but they all work in the same way: by combining with the still captive air, the insulation acts as a barrier to heat loss. Please note, in a few instances (such as for timber frame and system built dwellings e.g. steel frame) cavity wall insulation is not appropriate, please contact a CIGA registered installer for more information if you are in any doubt.

    How do I know if I have cavity walls?

    First of all, check the age of your house. In most houses built after the 1920s, the external walls are made of two layers with a small air gap or ‘cavity’ between them.


    Also, check the thickness of the walls by any entrance door or window. Cavity walls are at least 26.5cm (10.5 inches) thick.

    Looking at the brick pattern of your outside walls can also help to identify cavity walls, as this will usually differ from solid walls.

    Is it going to be costly?

    No. An average grant aided installation will cost around £260 and you’ll find that, with the savings you make on your heating bills, cavity wall insulation will pay for itself in under 2 years. Find out whether you’re eligible for a grant

    How long will it take?

    Between two to three hours for a three bedroom semi-detached house.

    Will it make a mess?

    No. The insulation is injected from the outside, so the installers will not be working in the house.

    What do they use as insulation?

    The material used will most likely be mineral wool or polystyrene beads. It will be properly accredited as a building material, guaranteed by the Cavity Insulation Guarantee Agency (CIGA), and will be installed by a certified contractor.

    Will the work meet regulations and be guaranteed?

    It is strongly recommended that you use a professional company. If you use a professional, the work will be guaranteed for 25 years by the Cavity Insulation Guarantee Agency (CIGA). A member of this Agency will be aware of building regulations and the CIGA guide to best practice.

    How can I find a registered installer?

    Contact your local Energy Efficiency Advice Centre on 0800 512 012 who will be able to give you information about installers and grant and offers in your area. Alternatively, contact the Cavity Insulation Guarantee Agency (CIGA) or the National Insulation Association (NIA).

    Where can I find more information about home insulation?

    Visit the National Insulation Association (NIA) for information on all types of home insulation – cavity wall insulation, loft insulation, draught proofing and internal flexible linings or call 01525 383313.

    How is it Installed?

    Getting your walls insulated couldn’t be easier. It can normally be applied from the outside through small holes, drilled in the wall by trained technicians. The material is then injected through the holes, filling the cavity. The holes are filled in to make as perfect a match as possible with the existing wall.

    It’s a simple process and is normally completed within three hours, without damage or mess to your house or garden.

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